MICROALGAE FROM FERMENTATIONS FOR FISH OIL REPLACEMENT

The primary lipid source used in aquaculture diets has been marine oil by-products of fish meal production since the development of compound feeds.  These marine oils are highly palatable with attractant qualities and historically were widely available at competitive prices.  However, in recent years, supplies of marine oils have remained constant as demand has increased, with aquaculture feeds now consuming 90% of the global fish oil supply .  In response to increased demand, marine oil prices have increased, which has spurred the search for alternative lipid sources capable of maintaining fish performance and nutritional value to consumers.  Fish is the main dietary source of long-chain polyunsaturated fatty acids (LC-PUFA), including eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), which play important roles in human neurologic, cardiac, vascular and reproductive health.

Single-cell organisms such as thraustochytrids, diatoms and microalgae offer novel, renewable sources of LC-PUFA from the marine environment.  Thraustochytrids are heterotrophic protists found in marine environments that were originally thought to be closely related to primitive fungi . More recent classification has aligned them with heterokont algae such as diatoms and brown algae . Thraustochytrids produce high levels of lipids containing a large percentage of omega-3 LC-PUFA.  Strain selection and optimum growing conditions have resulted in the production of thraustochytrid whole-cell products that are high in DHA, low in n-6 fatty acids, and have high omega n-3 to n-6 ratios .  Alltech ferments a single-celled algae,  Schizochytrium sp., for production  of a sustainable source of  DHA (All-G-Rich).  All-G-Rich has been successfully used to replace marine fish oil in the diets of Atlantic salmon Salmo salar , largemouth bass Micropterus salmoides and Pacific white shrimp Litopenaeus vannamei.  All-G-Rich can also be used to enrich the DHA levels of Nile tilapia Oreochromis niloticus.  The DHA rich algae All-G-Rich has been shown to be an effective alternative to fish oil as a feed ingredient.